Error when adding Keystore for SSL in Metabase Cloud

I am using Metabase cloud.

I am trying to set up a secure connection to Presto and failing. I create a Keystore (pks format) on my server where Presto is running, but when I try to add SSL in my Database connection in Metabase, it gives me an error:

Error setting up SSL: toDerInputStream rejects tag type 100

I googled that error and found a similar question on here, but the solution they reached seems to be for self hosted instances, and is not something I can do on cloud. (using the "Local File Path" option rather than using "Uploaded file path.")

Is .pks an accepted format for Metabase to use? Is there something I am missing? Is there a way for me to just use a .cer instead?

Edit: This is the question that had a similar issue, but does not resolve my current problem: Connecting to Prestodb - #3 by AlexBloor